472 CHEMICAL ENGINEERING The Leeds & Northrup Co. has developed a two-couple continuous curve recorder for automatically heating furnaces to definite temperatures. As applied in carburiz-ing and tempering of steel one thermocouple is placed in the furnace chamber and the other in contact with the steel piece. The controller automatically maintains the furnace for instance at 1,000°C. until the steel has reached 900°C. and then it drops the furnace to 900°C. Such an arrangement for control can be applied to a great many processes. BRIEF BIBLIOGRAPHY ON INDUSTRIAL PYROMETRY For a complete bibliography of pyrometry and allied subjects up to 1912, see second reference below. General Treatises Waidner, Mueller, Dickinson and Wilhelm, Thermo me try, Bureau of Standards, Sci. Paper in preparation. Burgess & Le Chatelier, "Measurement of High Temperatures," Wiley, 1912. Darling, "Pyrometry," Spon & Chamberlain, 1911. Ferry, Shook and Collins, "Practical Pyrometry," Wiley, 1917. Griffiths, "Methods of Measuring Temperatures," Griffin, 1918. Foote, Fairchild and Harrison, Pyrometric Practice, Bureau of Standards, Sci. Paper 170, 1921. Special References not Included in Above Adams, Tables for Pt-Rh and Cu-Constantan couples, Jour. Am. Chem. Soc., 36 January, 1914. Burgess and Foote, Radiation Pyrometry, Bureau of Standards, Sci. Paper 250, 1915. Burgess and Foote, Pyrometry, "Standard Handbook for Electrical Engineers," McGraw-Hill, 1922. Day, Sosman and Allen, High Temperature Gas Thermometry, Carnegie Inst. Pub. No. 157, 1911. Nitrogen thermometer to 1,550°C. and discussion of fixed temperature points from zinc to platinum. Fairchild and Schmitt, Life Tests of Platinum, Platinum-Rhodium Thermocouples, Chem. Met. Eng., 26, p. 158, 1922. Faraday Society Pyrometry Symposium, Trans. Faraday Soc., London, June, 1918. A collection of papers bearing on English pyrometric practice. Foote, Cold Junction Corrections for Thermocouples, Bureau of Standards, Sci. Paper 202, 1914. Foote, Harrison and Fairchild, Standardization of Thermocouples, Met. Chem. Eng., 18, p. 343, p. 403, 1918. Forsythe, Optical Pyrometry, G. E. Review, 20, p. 749, 1917. /. Opt. Soc. Am., 4, p. 305, 1920. Kowalke, Cobalt for Thermocouple, Am. Electrochem. Soc., April, 1916. Pyrometer Symposium. A collection of papers on American pyrometric practice published in Bull. Met. and Min. Eng., 1919-1920. Waidner and Burgess, Optical Pyrometry, Bureau of Standards, Sci. Paper 11, 1905. Waidner and Burgess, Platinum Resistance Thermometry, Bureau of Standards, Sci. Paper 124, 1909. Woodward and Harrison, Nichrome-constantan Thermocouple, Met. Chem. Eng., June 1, 1917.